Servomechanisms or servos are devices that use feedback or error-correction signals to control the desired operation of a mechanism. Servos typically include a motor (e.g., an electrical motor) that controls the angular orientation of an output shaft, which is in turn coupled to a movable control surface or component of a mechanical system. Servos generally function on the principle of negative feedback, where a control input is compared to the actual measured position of a mechanical system. Any difference between the actual and desired values (i.e., an “error signal”) is used to drive the system in the direction necessary to reduce or eliminate the error. Servos, for example, are commonly used in unmanned aircraft or air vehicles to precisely and dynamically position control surfaces such as elevators and rudders.
One concern with many conventional servos, however, is that the orientation of the output shaft relative to the motor when the output shaft is at a neutral or “commanded center” position can vary between individual servos because of manufacturing and/or installation discrepancies. To compensate for these variances, each servo must be individually calibrated to precisely position the output shaft at the desired neutral location. Such calibration processes can be extremely time-consuming and expensive. Another concern with many conventional servos is that such systems have a limited adjustment resolution. For example, a typical double output arm servo used with many unmanned aircraft has an adjustment resolution of approximately 7.2 degrees. This arrangement yields only 25 discrete adjustment positions per 180 degrees and, accordingly, only relatively coarse adjustments can be performed when calibrating the servo.